The period of time,

measured from the onset of an action potential,

during which another action potential cannot be

triggered.

The focusing of light by changing

the shape of the eye’s lens.

An amine that serves as a

neurotransmitter at many synapses in the peripheral

and central nervous systems, including the

neuromuscular junction.

A cytoskeletal protein in all cells and the major

thin fi lament protein in a skeletal muscle fi ber;

causes muscle contraction by specifi c chemical

interactions with myosin.

adenosine triphosphate (ATP)

The molecule that

is the cell’s energy source. The hydrolysis of ATP

to produce adenosine diphosphate (ADP) releases

energy that fuels most of the biochemical reactions

of the neuron. ADP is converted back to ATP in the

mitochondria.

adenylyl cyclase

An enzyme that catalyzes the

conversion of adenosine triphosphate (ATP) to

cyclic adenosine monophosphate (cAMP), a second

messenger.

The outer segment of the adrenal

gland; releases cortisol when stimulated by the

pituitary adrenocorticotropic hormone.

The inner segment of the adrenal

gland, innervated by preganglionic sympathetic

fi bers; releases epinephrine.

A catecholamine neurotransmitter

synthesized from norepinephrine; also called

epinephrine.

adrenocorticotropic hormone (ACTH)

A hormone

released by the anterior pituitary in response

to corticotropin-releasing hormone; stimulates the

release of cortisol from the adrenal gland.

A threatening or defensive

form of aggression accompanied by vocalizations

and a high level of ANS activity.

A psychiatric condition characterized

by disordered emotions; also called mood

disorder. Examples are major depression and

bipolar disorder.

The study of the neural

basis of mood and emotion.

An axon coursing toward and innervating a

given structure. See also efferent.

after-hyperpolarization

The hyperpolarization

that follows strong depolarization of the membrane;

the last part of an action potential, also called

undershoot.

The inability to recognize objects, even

though simple sensory skills appear to be normal;

most commonly caused by damage to posterior

parietal areas of the brain

A mental disorder characterized by

severe anxiety about being in situations in which

escape might be diffi cult or embarrassing.

A neuron that innervates the

extrafusal fi bers of skeletal muscle

A neuron in the retina of the eye that

projects neurites laterally in the inner plexiform

layer

A chemical building block of protein

molecules, containing a central carbon atom, an

amino group, a carboxyl group, and a variable R

group.

A severe loss of memory or the ability to

learn. See also anterograde amnesia, retrograde

amnesia.

A subtype of glutamate receptor; a

glutamate-gated ion channel that is permeable to

Naand K.

The bulge along a semicircular canal,

which contains the hair cells that transduce

rotation

An almond-shaped nucleus in the anterior

temporal lobe thought to be involved in emotion and

certain types of learning and memory.

The biosynthesis of organic molecules

from nutritive precursors; also called anabolic

metabolism. See also catabolism.

Male sex steroidal hormones, the most

important of which is testosterone.

A drug that treats the symptoms

of depression by elevating brain levels of monoamine

neurotransmitters; examples are tricyclics,

monoamine oxidase (MAO) inhibitors, and SSRIs.

antidiuretic hormone (ADH)

a partial or complete loss of language abilities following brain damage

see also Broca's aphasia, conduction aphasia, Wernicke's aphasia

basal forebrain complex

basal ganglia

binocular visual field

bipolar cell

bipolar disorder

bipolar neuron

blob

blob pathway

blood-brain barrier

bottom-up attention

brain

brain stem

Broca's aphasia

a language disturbance in which a person has difficulty speaking or repeating words but can understand language; also known as motor or nonfluent aphasia

Broca's area

bulimia nervosa

bundle

CA1

a region of Ammon's horn in the hippocampus that receives input from the neurons of CA3

CA3

a region of Ammon's horn in the hippocampus that receives input from the neurons of the dentate gyrus

calcium-calmodulin-dependent protein kinase 

(CaMK)

a protein kinase activated by elevations of internal Ca²⁺ concentration

calcium pump

cell-adhesion molecule

CAM

Cannon-Bard theory

a theory of emotion proposing that emotional experience is independent of emotional expression and is determined by the pattern of thalamic activation

capsule

a collection of axons that connect the cerebrum with the brain stem

cardiac muscle

a type of striated muscle found only in the heart; it contracts rhythmically even in the absence of innervation

catabolism

the breaking down of complex nutrient molecules into simpler molecules; also called catabolic metabolism

see also anabolism

catecholamines

these 3 neurotransmitters:

dopamine, norepinephrine, epinephrine

cation

a positively charged ion

see also ion

caudate nucleus

a part of the basal ganglia in the basal forebrain, involved in motor control

cholecystokinin

CCK

cell-adhesion molecule (CAM)

A molecule on the cell surface that causes cells to adhere to one another

cell assembly

a group of simultaneously active neurons that represents an object held in memory

cell body

the central region of the neuron containing the nucleus; also called soma or perikaryon

center-surround receptive field

a visual receptive field with a circular center region and a surround region forming a ring around the center; stimulation of the center produces a response opposite that generated by stimulation of the surround

central nervous system (CNS) 

the brain (including the retinas) and spinal cord. 

see also peripheral nervous system

central pattern generator

a nerual circuit that gives rise to rhythmic motor activity

central sulcus

the sulcus in the cerebrum that divides the frontal lobe from the parietal lobe

cerebellar cortex

a sheet of gray matter lying just under the pial surface of the cerebellum

cerebellar granule cell

a neuron in the cerebellar cortex that receives input from mossy fibers and gives rise to parallel fibers that innervate Purkinje cells. Plasticity of the synapses between granule cells and Purkinje cells is believed to be important for motor learning.

cerebellar hemispheres

the lateral regions of the cerebellum

cerebellum

a structure derived from the rhombencephalon, attached to the brain stem at the pons; an important movement control center

cerebral aqueduct

a canal filled with cerebrospinal fluid within the midbrain

cerebral cortex

the layer of gray matter that lies just under the surface of the cerebrum

cerebral hemispheres

the two sides of the cerebrum, derived from the paired telencephalic vesicles

cerebrospinal fluid (CSF)

in the CNS, the fluid produced by the choroid plexus that flows through the ventricular system to the subarachnoid space

cerebrum

the largest part of the forebrain; also called telencephalon

cyclic guanosine monophosphate

cGMP

channelopathy

channelrhodopsin-2 (ChR2)

a light-sensitive cation channel, originally isolated from green algae, which can be expressed in neurons and used to control their activity using light

characteristic frequency

the sound frequency to which a neuron in the auditory system gives its greatest response

chemical synapse

a synapse in which presynaptic activity stimulates the release of neurotransmitter, which activates receptors in the postsynaptic membrane 

chemoaffinity hypothesis

the hypothesis that chemical markers on growing axons are matched with complementary chemical markers on their targets

chemoattractant

chemoreceptor

any sensory receptor selective for chemicals

chemorepellent

a diffusible molecule that acts over a distance to repel growing axons

cholecystokinin (CCK)

cholinergic

describing neurons or synapses that produce and release acetylcholine

chromosome

a structure in the cell nucleus containing a single linear thread of DNA

ciliary muscle

a muscle that controls the shape of the eye's lens

circadian rhythm

any rhythm with a period of about 1 day

classical conditioning

a learning procedure in which a stimulus that evokes a measurable response is associated with another stimulus that normally does not evoke this response

climbing fiber

an axon of an inferior olive neuron that innervates a Purkinje cell of the cerebellum. Climbing fiber activity is an important trigger for LTD, a form of synaptic plasticity believed to be important for motor learning

clock gene

a gene that is critically involved in the molecular mechanism of the circadiam rhythm; clock genes are translated into proteins that regulate their own transcription, and their expression rises and falls over a cycle of about 24 hours

cochlea

a spiral bony structure in the inner ear that contains the hair cells that transduce sound

cochlear amplifier

outer hair cells, including the motor proteins in the outer hair cell membrane, that amplify displacements of the basilar membrane in the cochlea

cochlear nucleus

see dorsal cochlear nucleus, ventral cochlear nucleus

cognitive map theory

the idea that the hippocampus is specialized to form a spatial map of the environment

color-opponent cell

a cell in the visual system with an excitatory response to wavelengths of light of one color and an inhibitory response to wavelengths of another color; the color pairs that cancel each other are red-green and blue-yellow

commissure

any collection of axons that connect one side of the brain with the other side

complex cell

a type of visual cortical neuron that has an orientation-selective receptive field without distinct ON and OFF subregions

concentration gradient

a difference in concentration from one region to another. ionic concentration gradients across the neuronal membrane help determine the membrane potential

conduction aphasia

a type of aphasia associated with damage to the arcuate fasciculus, characterized by good comprehension and speech but difficulty repeating words

cone photoreceptor

a photoreceptor in the retina containing one of three photopigments that are maximally sensitive to different wavelengths of light; concentrated in the fovea, specialized for daytime vision, and responsible for all color vision 

conjunctiva

the membrane that folds back from the eyelids and attaches to the sclera of the eye

connectome

a detailed wiring diagram of how neurons connect with one another via synapses

consciousness

awareness of external stimuli and internal thoughts and feelings

contralateral

an anatomical reference meaning on the opposite side of the midline

cooperativity

the property of long-term potentiation, reflecting the requirement that many inputs be active at the same time during a tetanus to induce LTP 

see also long-term potentiation

cornea

the transparent external surface of the eye

coronal plane

an anatomical plane of section that divides the nervous system into anterior and posterior parts

corpus callosum

the great cerebral commissure, consisting of axons connecting the cortex of the two cerebral hemispheres

cortex

any collection of neurons that forms a thin sheet, usually at the brain's surface

cortical module

the unit of cerebral cortex that is necessary and sufficient to analyze one discrete point in a sensory surface

cortical plate

a cell layer of the immature cerebral cortex containing undifferentiated neurons

cortical white matter

a collection of axons lying just below the cerebral cortex

corticospinal tract

the tract that originates in the neocortex and terminates in the spinal cord; involved in the control of voluntary movement

corticotropin-releasing hormone (CRH)

a hormone released by neurons in the paraventricular nucleus of the hypothalamus; stimulates the release of ACTH from the anterior pituitary

cortisol

a steroid hormone released by the adrenal cortex; mobilizes energy reserves, suppresses the immune system, and has direct actions on some CNS neurons

co-transmitter

one of two or more different neurotransmitters that are released from a single presynaptic nerve terminal

cranial nerves

twelve (12) pairs of nerves that arise from each side of the brain stem, numbered from anterior to posterior. 

__I is actually the olfactory tract, and __II is the optica nerve; both are parts of the CNS. __III-XII, which are in the PNS, perform many diverse functions

corticotropin-releasing hormone

CRH

critical period

a limited of time when a particular aspect of brain development is sensitive to a change in the external environment

cerebrospinal fluid

cyclic adenosine monophosphate 

(cAMP)

a second messenger formed frmo adenosine triphosphate by the action of the enzyme adenylyl cyclase

cyclic AMP response element binding protein 

(CREB)

a protein that binds to specific regions of DNA (cyclic AMP response elements) and functions to regulate gene transcription; a key regulator of protein synthesis-dependent memory consolidation

cytoarchitectural map

a map, usually of the cerebral cortex, based on

differences in the arrangement of neuronal cell bodies in various parts of the brain 

cytoarchitecture

the arrangement of neuronal cell bodies in various parts of the brain 

cytochrome oxidase

a mitochondrial enzyme concentrated in cells that form the blobs in primary visual cortex

cytoplasm

cellular material contained by the cell membrane, including the organelles but excluding the nucleus

cytoskeleton

the internal scaffolding that gives a cell its characteristic shape; consists of microtubules, neurofilaments, and microfilaments

cytosol

the watery fluid inside a cell

Dopamine

DA

diacylglycerol

DAG

Dale's principle

the idea that a neuron has a unique identity with respect to neurotransmitter

dark adaptation

the process by which the retina becomes more sensitive to light in dim light

dark current

the inward sodium current that occurs in photoreceptors in the dark

declarative memory

memory for facts and events

default mode network

an interconnected group of brain areas that are consistently more active when the brain is at rest than during active behavioral tasks

delayed non-match to sample (DNMS)

a behavioral task in which animals are trained to displace one of two alternative objects that does not match a previously seen sample object

dendrite

a neurite specialized to receive synaptic inputs from other neurons

dendritic spine

a small sac of membrane that protrudes from the dendrites of some cells and receives synaptic input

dendritic tree

all the dendrites of a single neuron

see secretory granula

dense-core vesicle

dentate gyrus

a layer of neurons in the hippocampus that receives input from the entorhinal cortex

deoxyribonucleic acid

DNA

depolarization

a change in membrane potential, taking it from the value at rest (e.g., -65mV) to a less negative value (e.g., 0 mV)

dermatome

 a region of skin innervated by the pair of dorsal roots from one spinal segment

diaclyglycerol (DAG)

a second messenger molecule formed by the action of phospholipase C on the membrane phospholipid phosphatidylinositol-4, 5-biphosphate; this messenger molecule activates the enzyme protein kinase C

diathesis-stress hypothesis of mood disorders

a hypothesis suggesting that depression is caused by a combination of genetic predisposition and environmental stress

diencephalon

a region of the brain stem derived from the prosencephalon (forebrain). these structures include the thalamus and hypothalamus

differentiation

During embyonic development, the process by which structures become more complex and functionally specialized

diffuse modulatory system

one of several systems of CNS neurons that project widely and diffusely onto large areas of the brain adn use modulatory neurotransmitters, including dopamine, norepinephrine, serotonin, and acetylcholine

diffusion

the temperature-dependent movement of molecules from regions of high concentration to regions of low concentration, resulting in a more even distribution

dimensional theories of emotion

explanations of emotions in which each emotion is built from emotional components such as level of arousal and emotional strength

diopter

a unit of measurement for the refractive power of the eye; the reciprocal of the focal distance

direction selectivity

the propertty of cells in the visual system that respond only when stimuli move within a limited range of directions

distal muscle

a muscle that controls the hands, feet, or digits

distributed memory

the concept that memories are encoded by widespread synaptic modifications of many neurons, not by a single synapse or cell

DNA (deoxyribonucleic acid)

a double-stranded molecule constructed from four nucleic acids that contains the genetic instructions for a cell

dopa

a chemical precursor of dopamine and the other catecholamines

dopamine (DA) 

a catecholamine neurotransmitter synthesized from dopa (l-dopa)

dopamine hypothesis of schizophrenia

a hypothesis suggesting that schizophrenia is caused by excessive activation of D2 receptors in the mesocorticolimbic dopamine system in the brain

dorsal

an anatomical reference meaning toward the back

dorsal cochlear nucleus

a nucleus in the medulla that receives afferents from the spiral ganglion in the cochlea of the inner ear

dorsal column-medial lemniscal pathway

an ascending somatic sensory pathway that mediates information about touch, pressure, vibration, and limb proprioception

dorsal column nucleus

one of a pair of nuclei located in the posterior medulla; target of dorsal column axons, mediating touch and proprioceptive input from the limbs and trunk

dorsal horn

the dorsal region of the spinal cord containing neuronal cell bodies

dorsal longitudinal fasciculus

a bundle of axons reciprocally connecting the hypothalamus and midbrain periaqueductal gray matter

dorsal root

a bundle of sensory neuron axons that emerges from a spinal nerve and attaches to the dorsal side of the spinal cord; these axons bring information into the spinal cord

dorsal root ganglion

a collection of cell bodies of the sensory neurons that are part of the somatic PNS; only one of these for each spinal nerve

duplex theory of sound localization

the principle that two schemes function in sound localization: interaural time delay at low frequencies and interaural intensity difference at high frequencies

dura mater

the outermost of the three meninges, the membranes that cover the surface of the CNS

dyslexia

difficulty learning to read despite normal intelligence and training

easy problems of consciousness

phenomena related to consciousness that can be studied by scientific methods; not the problem of the neural basis of conscious experience

electroencephalogram

EEG

efferent

an axon originating in and coursing away from a given structure

electrical conductance

the relative ability of an electrical charge to migrate from one point to another, represented by the symbol g and measured in siemens (S); it is the inverse of resistance and is related to electrical current and voltage by Ohm's law

electrical current

the rate of movement of electrical charge, represented by the symbol I and measured in amperes (amp/amps)

electrical potential

the force exerted on an electrically charged particle, represented by the symbol V and measured in volts; also called voltage or potential difference

electrical resistance

electrical self-stimulation

electrical stimulation that an animal can voluntarily deliver to a portion of its brain

electrical synapse

a synapse in which electrical current flows directly from one cell to another via a gap junction

electroconvulsive therapy (ECT)

a treatment for major depression that involved eliciting electrical seizure activity in the brain

electroencephalogram (EEG)

a measurement of electrical activity generated by the brain and recorded from the scalp

endocannabinoid

a natural (endogenous) chemical that binds to, and activates, cannabinoid (CB) receptors

endocochlear potential

the voltage difference between the endolymph and the perilymph, about 80 mV

endocytosis

the process by which a bit of the cell membrane is pinched off, internalized, and converted to an intracellular vesicle

endogenous attention

attention voluntarily directed by the brain to serve a behavioral goal; also called top-down attention

endolymph

the fluid that fills the scala media in the cochlea of the inner ear, containing high K⁺ and low Na⁺ concentrations

endorphin

one of many endogenous opiod peptides with actions similar to those of morphine; present in many brain structures, particularly those related to pain

engram

the physical representation or location of a memory; also called a memory trace

enteric division

a division of the automatic nervous system that innervates the digestive organs; consists of the myenteric and submucous plexuses

entorhinal cortex

a cortical region in the medial temporal lobe that occupies the medial bank of the rhinal sulcus; provides input to the hippocampus

ependymal cell

a type of glial cell that provides the lining of the brain's ventricular system

ephrin

a protein secreted by neurons in many parts of the developing nervous system that helps establish topographic axonal connections

epilepsy

a chronic brain disorder characterized by recurrent seizures

epinephrine

a catecholamine neurotransmitter synthesized from norepinephrine; also called adrenaline

excitatory postsynaptic potential

EPSP

EPSP summation

a simple form of synaptic integration whereby excitatory postsynaptic potentials combine to produce a larger postsynaptic depolarization

estrogens

female steroidal hormones, the most important of which are estradiol and progesterone

estrous cycle

eustachian tube

an air-filled tube connecting the middle ear to the nasal cavities

excitable membrane

any membrane capable of generating action potentials. the membrane of axons and muscle cells is excitable

excitation-contraction coupling

the physiological process by which the excitation of a muscle cell leads to its contraction

excitatory postsynaptic potential (EPSP)

depolarization of the postsynaptic membrane potential by the action of a synaptically released neurotransmitter

exocytosis

the process whereby material is released from an intracellular vesicle into the extracellular space by fusion of the vesicle membrane with the cell membrane

exogenous attention

attention reflexively directed to an external stimulation because of its salience; also called bottom-up attention

extension

the direction of movement that opens a joint

extensor

a muscle that causes extension when it contracts

extracellular matrix

the network of fibrous proteins deposited in the space between cells

extrafusal fiber

a muscle fiber in skeletal muscle that lies outside muscle spindles and receives innervation from alpha motor neurons

extraocular muscle

a muscle that moves the eye in the orbit

falling phase

the part of an action potential characterized by a rapid fall of membrane potential from positive to negative

fasciculation

a process in which axons growing together stick to one another

fast motor unit

a motor unit with a large alpha motor neuron innervating rapidly contracting and rapidly fatiguing white muscle fibers

flexion

the direction of movement that closes a joint

a muscle that causes flexion when it contracts

follicle-stimulating hormone (FSH)

a hormone secreted by the anterior pituitary; its diverse roles include the growth of follicles in the ovaries and the maturation of sperm in the testes

forebrain

the region of the brain derived from the rostral primary embryonic brain vesicle; also called prosencephalon. Forebrain structures include the telencephalon and the diencephalon. 

fornix

a bundle of axons that originates in the hippocampal formation, loops around the thalamus, and terminates in the diencephalon

fourth ventricle

the CSF-filled space within the hindbrain

fovea

the pit or depression in the retina at the center of the macula; in humans, the fovea contains only cone photoreceptors and is specialized for high-acuity vision. 

frequency

the number of sound waves or other discrete events per second, expressed in hertz (Hz)

frontal eye field (FEF)

a cortical area in the frontal lobe involved in the generation of the saccadic eye movements

frontal lobe

the region of the cerebrum lying anterior to the central sulcus under the frontal bone

frontoparietal attention network

a group of interconnected brain areas involved in guiding visual attention

follicle-stimulating hormone

FSH

gamma-aminobutyric acid

GABA